Fossil fuel is a finite resource, the burning of which has incipient environmental consequences. An increase in the use of alternative energy sources is desirable, as is better efficiency in the use of all energy. Photovoltaic generation of electricity is a broad, high tech energy source but still has limitations with respect to scale and storage.
Solar interior illumination is a relatively low tech alternative source, and offers huge saving in terms of fossil fuel. Except for window panes and sky lights, however, interior solar lighting has been clumsy, costly and difficult because both the intensity and the angles of sunlight vary so widely with time of day, with the seasons, and with the weather. Meanwhile, lighting systems which use a lot of electricity while the sun shines are almost universal.
One improvement in the use and distribution of light has come with the inventions disclosed in U.S. Pat. No. 6,014,489 owned by the Ply-Light Corporation of Saint Paul Minn. and sold under the trademark Ply-Light. The tubes receive substantially collimated light and distribute it efficiently over large areas in the form of diffused i.e. uncollimated, light. The Ply-Light® tubes distribute artificial light which starts life inherently uncollimated. Since these tubes work best if their inputs are in the form of substantially collimated light, one aspect of the present invention addresses the technology for converting uncollimated artificial light sources to substantially collimated light for more efficient use in the new tubes.
The technology for making artificial light is improving with new, powerful, energy-efficient light sources such as metal halide-based electric lamps as well as small glass envelopes filled with gaseous sulphur compounds that virtually burst into luminescence in the presence of a microwave electromagnetic field. The basic appeal is savings in fuel required to make the electricity to power the new lights. Since the new light sources are centralized and can use light-distributing tubes, they can also eliminate some labor-intensive and costly procedures such as installing many discrete, heat-generating electric light fixtures, to say nothing of the life time chore of changing many dead bulbs and fluorescent tubes, often in inaccessible places, and disposing of them safely.
So single lighting systems which can efficiently distribute either solar light when the sun shines or controllable artificial light through the same tubes when sufficient sunlight is not available, will have appeal to the environmentalist and economist alike. The various aspects of the present invention are directed to this new technology. The new high-intensity light sources, however, crave better and more efficient means of distribution.